dsa2 min read
Valid Anagram — Frequency Array vs HashMap [Amazon, Google Easy]
Check if two strings are anagrams — same characters with same frequencies. Two O(n) approaches: 26-int array for lowercase, HashMap for Unicode.
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Frequency-count
2 articles
dsa2 min read
First Unique Character in String — Two-Pass Frequency Map [Amazon Easy]
Find the index of the first non-repeating character in a string. Two-pass O(n) solution with a 26-array or HashMap.
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